Dry cleaning



Patented ct. 21,. 13$

LLOYD E. .mcxson, or PITTSBURGH, rnuns'rnvan DRY cLnanmc No Drawing.

1 wood or metal, mounted horizontally on trunnions and enclosed in a wood or metal shell. Naphtha put into. the washer is retained by the outer shell. The hollow cylinder and the outer shell are fitted with suitable doors so that the articles may be placed in and removed from the cylinder. The cylind'er when in operation is mechanically rotated back and forth, a few turns one direction, and a few turns the opposite direction alternately. The agitation produced in this manner causes the dirt to be removed by the naphtha from the articles.

The mai or portion of the dirt in the articles is easil removed. Some of the soil, food spots, etc.,however, may remain. and 'these can be removed only with the aid of special detergents. Dry-cleaning soapis used for this purpose. There are two distinct types of dry-cleaning soap used in practice. One type contains a mixture of partially saponified fatty acids, organic solvents, and water: the other tvne contains a mixture of com letely saponified fatty acids, organic solvents, and

i water. The alkali commonly used for saponifying the fatty acids may be either any one of. or a mixture of, the following: sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium & aluminate. Other alkaline substance which will produce saponification of the fatty acid maybe used to prepare the dry-cleaningsoap. Dry'cleaning may be conducted as a batch process or asqa continuous process. The

batch method consists Of introducing the batches.

Application filed April 8, 1929. Serial No. 853,685.

soiled articles to be cleaned into a measured. batch of naphtha in a washer, and then operating the Washer for a period of time, usually from 5 to 30 minutes. After therun in the washerthe naphtha and the dirt and dissolved matter it contains are removed from the washer. In some dry-cleaning plants a run of a given quantity of articles in two batches of naphtha successively is considered sufficient; in other plants the materials may be subiected to treatment in fresh batches of naphtha ranging from one to six in number.

- Dry-cleaning soap is usually added either to the first or to the second batch of naphtha, and sometimes to the second and third After the articles have been given. what is considered a suflicient number of runs in the washer, they are removed from the washer and placed in a centrifugal extractor, where the inaj or portion of the naphtha. contained in them is removed. The remaining naphtha may then be removed by allowing the articles to hang in heated rooms,-or by placing them in drying-tumblers. Finally, any

spots not removed by the treatment in the washers are by additional, localized treatment removed and the articles are pressed or finished in some other suitable manner. The naphtha used in the batch method of cleaning is collectedas it is taken from the washer and it is recovered for use again by methods known to the industry. 1 Y

In the continuous process the mechanical procedure is the same as in the batch method. The difference between the batcli method and the continuous methodis that in the latter one larger quantity of naphtha is caused to circulate through the washer, thence through a, purifying, apparatus, and then back into The purifying apparatus may consist of a still or of a caustic treating unit together ramie, or other fibre; and other materials,-

not woven, as for example fur, feathers; in

' short,.fibrous material of all sorts.

It has been found that dry-cleaned articles often acquire after a short period of timesay'of two or threeweeksa disagreeable, rancid odor; and this disagreeable odor has been found to be due to the oxidizing of fatty acids, traces of which present in the dry-cleaning soap, have remained in the articles. In order to avoid this undesirable odor, it is becoming a practice in the dry-cleaning industry to use completely-saponified soaps containing no free fatty acid, especially in the continuous processof cleaning. Even so the difficulty is not completely overcome, and the disagreeable odor may yet develop, in spite of preventive care.

When a completely saponified soap is used in continuous process, it is common practice to use a method for purifying the naphtha during the continuous run in which -only suspended matter is removed from it, leaving the soluble substances, including the drycleaning soap, in solution. The soapy bath is used continuously to clean successive loads of materials. The materials are removed from the bath, centrifuged, and dried. The soap dissolved in the small amount of naphtha remaining in the-materials after centrifuging is left as a residue inthem. The soapy bath is used over and over again and it is necessary to make small additions of soap with each load of materials cleaned.

I have discovered that the hitherto uncorrected difficulty is to be found in the articles themselves; I have found that they often containappreciable quantities of acid; that the acid sopresent, reacting with the soap will eflect the release of free fatty. acid, even though initially saponification had been complete; and that the so'released acid does in particular cases, and after repeated loads of material have been cleaned, become the immediate cause of a rancid odor. I

have discovered, furthermore, that by the decomposition of the soap and the gradual building up of free fatty acid in the bath, the detergent power of the soap is weakened and that some of the water in the dry-cleaning soap is selectively absorbed by the texis a needless waste of the that the quantity of alkali and water required for the purpose of rejuvenating the soap in the bath be carefully determined by a chemical test, and only such quantities of alkali and of. w ater be added as will restore the detergent power of the soap. If too much alkali be added it will coagulate the soap, with the result that soap will as the continuous operation progresses be removed from the bath. If too little alkali be added, the full detergent value of'the soa will not be restored. If too much water added,

it will both cause a flocculation'of the soap and will cause the materials which are being cleaned to become wet with water.

. I determine the quantity of alkali which will be required to neutralize the free fatty acids in the bathby titrating a measured quantity of the used soapy naphtha from the dry-cleaning bath with standard caustic solution, by methods known to any chemist.

In my experimental work a 100 c. 0. portion of the used naphtha was titrated with 0.03 normal caustic soda solution in the presence of 50 c. o. of neutralized alcohol, using phenolphthalein as an indicator. It was found thatthe alkali subsequently added to the bath should be no more or less than that required to. keep the titration of 100 c. c. of the bath between 4 c. c. and 12 c. c. of 0.03 normal caustic solutions. If the bath be so far neutralized that less than 4 c. c. are required for the titration, there is a tendency for the soap to fiocculate, and in consequence to be removed from the bath by the purification process; if the neutralization be so far incomplete that more than 12 c. c. are required for the titration, there possible detergent power of the soap.

The alkali used for rejuvenating the soap in the dry-cleaning bath may be any of those previously mentioned as being suitable for the preparation of dry-cleaning soap.

The quantity of water required for rejuvenating the dry-cleaning'soap, was determined by a series of "distillations of the soapy dry-cleaning bath. The water .required is proportional to the weight of materials cleaned. Approximately 1 quart of Water was found necessary for each 150 v perimentation it is practiced commercially.

Four hundred gallons of petroleum naphtha are introduced into a system consisting of awasher, a purifying unit (which may be a filter or a centrifugal clarifier or separator),

a pump, and pipes connecting these parts.

Three gallons of completely saponitied soap are added to the naphtha. One hundred and fifty pounds of garments to be cleaned are placed in the washer. The washeris operdated for 25 minutes, during which time the V' which consists in testing quantitatively for soapy naphtha is pumped continuously from the Washer to the purifying unit and back to the washer again. Near the end of the run, say. after 20 minutes of operation, a sample of the soapy naphtha is removed from the machine. 100 c. c. of the sample are measured and titrated with a 0.03 normal caustic soda solution. The quantity of .caustic solution required for the test may be 7.0 c. c. Then as soon as the 25-minute run is completed, the cleaned garments are removed and another. load weighting 150 pounds is introduced into the washer, when another 25-minute run is started. A pint of potassium carbonate solution, prepared by dissolving 35 pounds of potassium carbonate in 16 gallons of water, and a pint of water are mixed together and poured into the washer while it is running. After the second run has been in progress for 20 minutes a second sample of the soapy naphtha is removed. The titration on 100 c. c. of the sample may be 100. c. of 0.03 normal caustic solution. Then in the following run 2 pints of the caustic solution may be added to the washer. The titration on a 100 c. 0. sample of the soapy naphtha after this run may be only 6 c. c. of 0.03 normal caustic soda solution. Then in the succeeding run a half pint of the potassium carbonate solution and one and one-half pints of water may be added to the bath. In this manner the acidity of the cleaning bath is controlled, so that the titration on 100 c. c. of the bath is kept between 4 c. c. and '12 c. c. of 0.03 normal caustic solution.

I claim as my invention:

1. In the'operation of dry-cleaning by the repeatedapplication of soap-bearing naphtha the method herein described of restoring to the used naphtha its detergent power free acid a sample taken from such body of used soap-bearing naphtha, and adding,

alkali to the body of used soap-bearing naphtha in quantities suflicient to saponify completely all free fatty acid, as determine by such testing.

2. In the operat1on of dry-cleaning in continuousmanner the method herein described of maintaining the quality of the circulating stream of soap-bearing naphtha which con- I sists in testing quantitatively for free acid a sample'taken from the circulating stream after the cleaning operation has been in progress, and adding alkali to the stream in quantity sufi'icient to restore the naphtha to its original condition as determined by such test.

3. In the operation of dry-cleaning incon 'tinuous manner the method herein described of maintaining the quality of the circulating stream of soap-bearing naphtha which consists in testing quantitatively for free acid and for water samples taken from the cir culating stream after the cleaning operation sufficient to restore the body of used soapbearing naphtha to its original condition, as

determined by such testing.

In testimony whereof I have hereunto set In hand. y LLOYD E. JACKSON. 

